Raman scattering in transition metal dichalcogenides MTe2 (M = Mo, W)

TL;DR

This study uses polarized Raman scattering and first-principles calculations to identify phonon modes in MoTe2 and WTe2, revealing detailed lattice dynamics and contributing to understanding their large magnetoresistance.

Contribution

It provides a comprehensive identification of Raman-active phonon modes in different phases of MoTe2 and WTe2 using combined experimental and theoretical approaches.

Findings

Identified 15 Raman-active modes in high-symmetry phase MoTe2

Observed all symmetry-allowed modes in low-symmetry phases

Enhanced understanding of lattice dynamics in transition-metal dichalcogenides

Abstract

We performed comparable polarized Raman scattering studies of MoTe2 and WTe2. By rotating crystals to tune the angle between the principal axis of the crystals and the polarization of the incident/scattered light, we obtained the angle dependence of the intensities for all the observed modes, which is perfectly consistent with careful symmetry analysis. Combining these results with first-principles calculations, we clearly identified the observed phonon modes in the different phases of both crystals. Fifteen Raman-active phonon modes (10Ag+5Bg) in the high-symmetry phase 1T'-MoTe2 (300 K) were well assigned, and all the symmetry-allowed Raman modes (11A1+6A2) in the low-symmetry phase Td-MoTe2 (10 K) and 12 Raman phonons (8A1+4A2) in Td-WTe2 were observed and identified. The present work provides basic information about the lattice dynamics in transition-metal dichalcogenides and may shed some light on the understanding of the extremely large magnetoresistance (MR) in this class of materials.